Fun with Fraunhofer

Abstract

Fraunhofer diffraction and interference by single and multiple apertures may be readily demonstrated using low-powered He-Ne lasers such as those increasingly found in schools. These qualitative demonstrations can become far more instructive if accompanied by quantitative measurements of the intensity distribution across the pattern which are obtained using a photodiode and a simple circuit. For observation of multislit interference, it has been found necessary to limit the diode aperture to 0.5 mm by fixing two pieces of PVC tape across the front.